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CHAPTER 6. USE CASES

This section highlights a few CAVe-in-a-box uses cases. CAVe-in-a-box supports many CAV applications, some of which are presented here for reference. Applications supported by CAVe-in-a-box include, but are not limited to, emergency vehicle preemption, PSM, and work zone TIMs. CAVe-in-a-box also supports hardware-in-the-loop (HIL) scenarios. Supported applications are described below with the CAVe-in-a-box perspective of how they can be tested.

EMERGENCY VEHICLE PREEMPTION

This use case allows the testing and teaching of emergency vehicle preemption application in the field. The requirements for this application to function properly include the following:

• A CAVe-in-a-box infrastructure kit installed on a roadway or test track. If the test track has no access to an intersection, then CAVe-in-a-box can be mounted on the side of the road and implemented as a virtual intersection for testing purposes.
• A CAVe-in-a-box mobile kit installed on a test vehicle. The preemption application requires sirens and lights to be enabled and associated with the BSM. Therefore, the mobile kit needs to be configured for this purpose. Some OBU vendors have made sirens and lights available through minimum configurations, so it is recommended that the user refer to the manuals when required.
• The TSC in CAVe-in-a-box must be configured to enable preemption and have preset plans for preemption with which to act.
• A signal head to see the traffic light status.

The use case progresses as follows: A vehicle equipped with a mobile kit broadcasting BSMs with extended fields encapsulating sirens and light status drives towards the infrastructure kit mounted on a test track. The vehicle is approaching the infrastructure kit in phases 2 and 4, where the initial setting of the signal heads has RED lights on phase 2. This testing demonstrates that, as the vehicle approaches within the DSRC or C-V2X range of the RSU installed in the infrastructure kit, the presence of sirens and lights on the BSM triggers a preemptive phase change in the TSC. The extended BSM containing sirens and light status is processed by V2X Hub, and the preemption signal is passed onto the TSC. The TSC, upon receiving the preemption call, uses the preset tables and changes the phases in 2 to be GREEN while pushing RED on all other phases—thereby allowing the emergency vehicle with sirens and lights to move through the intersection with minimum delay.

HARDWARE-IN-THE-LOOP SIMULATION

One of the interesting scenarios for CAVe-in-a-box is the HIL test case (Ma et al., 2018). This use case is appropriate for classroom or lab instruction, where the availability and logistics for a test track and outside testing may not always be feasible. In this test case, CAVe-in-a-box is used as a real interface for a simulation. Many traffic simulation software have interfaces that allow information to be exchanged with the outside world. A traffic simulation of an intersection can be made more interesting if the SPaT messages from the simulated intersections can be broadcasted from a real TSC, or a real TSC’s SPaT messages could be broadcasted to the virtual vehicles in a simulated environment. In addition, the BSMs from virtual vehicles can be broadcasted through the RSU so other mobile kits can receive them for educational purposes. CAVe-in-a-box can be the most important component in an educational toolkit that teaches students about ITS in a classroom setting.

PEDESTRIAN SAFETY

Pedestrian safety is a critical part of the ITS (USDOT, 2020). There have been various attempts at improving pedestrian safety using technology, including pedestrian detection cameras, Light Detection and Ranging (LiDAR), and PSM broadcast, among others. The need to enhance safety for pedestrians and other vulnerable road users led to the development of the Pedestrian application on V2X Hub.

CAVe-in-a-box can support pedestrian safety applications, such as by generating a PSM through the Pedestrian application available on V2X Hub. The PSM is created using data received from a nomadic device in the pedestrian’s possession, such as a cell phone. An application on the nomadic device is used to generate the data that will be used to create an SAE J2735 PSM using V2X Hub on CAVe-in-a-box. The data generated on the nomadic device will include the position, speed, and heading of the pedestrian, among other information. The data will be encoded in the XML format and sent to a public-facing web server created by V2X Hub using the available network connection, like cellular or Wi-Fi. The data may be generated at a frequency of 100 Hz to 1Hz, depending on the configuration.

The data received on V2X Hub will then be pared and converted into an unaligned packet encoding rules (UPER)-encoded SAE J2735 PSM through the Pedestrian application. This message will subsequently be relayed to the designated port on the RSU for immediate forward. The RSU will add the necessary security headers and forward the message over the available radio interface.

PSMs for each individual will have a unique identification number, and vehicles approaching the intersection equipped with CAVe-in-box will receive these messages through the wireless interfaces. The OBUs on these vehicles can subsequently warn the driver if there are any potential safety concerns by comparing the relative trajectory of pedestrian movement to that of the vehicle. The development of such an application for the OBU will be done at the discretion of the OBU manufacturers.

Additional enhancements to the pedestrian safety use case include adding a network backhaul to the CAVe-in-a-box installation in the event of multiple connected intersections, and adding a message distribution system developed at the discretion of the agency responsible for the infrastructure. This distribution system hosts a master web server for receiving PSM data within the jurisdiction. It will then be responsible for sending the PSM data received from the nomadic device to the web server for a particular CAVe-in-a-box system that is most relevant to the position of the pedestrian.

WORK ZONE

Work zone safety (USDOT, Work Zone Data Exchange [WZDx], 2020) is very important when it comes to freeway applications for CAVe-in-a-box. There is a need for improved safety at active work zones. Vehicles traveling at generally higher speeds on freeways are at a risk of causing critical accidents. An FHWA study concluded that there are around 773 deaths in work zone crashes every year (USDOT Work Zone Management Project, 2020). Various efforts to improve work zone safety are underway. One such effort led to the development of the SAE J2735 TIM. TIMs provide the opportunity to inform drivers about existing work zones using available radio communications. To enable this feature, this project developed the work zone safety application in V2X Hub.

A TIM includes the geometry of the applicable work zone and could also provide information regarding speed regulations or other road warnings using a combination of a Manual on Uniform Traffic Control Devices code and an International Traveler Information System code. This provides the opportunity to create a message that could inform the driver about the location of the work zone, the diversion to be used, and the speed regulations while driving through the diversion. This will also enhance the ability of CAVs to safely navigate around a work zone.

The TIM may be created using the USDOT TIM message creator tool, which is available as an open source resource. This tool will allow the user to draw the TIM over a geographical map by adding surveyed points, thus allowing for an accurate geometry. The message may then be converted into an XML structure for the work zone safety application in V2X Hub. A sample XML structure is available on the V2X Hub GitHub page. In addition to the elements of the TIM, the XML structure also requires start and stop broadcast times to ensure that the message is sent out only within a designated time period. Once the complete XML structure is ready, it may be sent to a web server available on V2X Hub specifically for the work zone application. Alternatively, a TIM XML may also be copied to the persistent memory of the V2X Hub computer in CAVe-in-a box and the start and stop broadcast times may be manually configured. Once a TIM XML is received by the work zone application, V2X Hub will encode the message into the SAE J2735 UPER and send it to the RSU for broadcast. The TIM will then be received by the OBU on the vehicle and may provide warnings to the driver depending on the applications available on the OBU.

The ability to send the TIM to a remote web server makes it possible for the message to be modified or updated through the TMC. Such a centralized system also helps with the integration of work zone data through other USDOT initiatives, including the use of a Situation Data Exchange (SDX) and the Work Zone Data Exchange (WZDx) programs. However, care must be taken to ensure that any modifications to the work zone elements have undergone rigorous verifications to ensure consistency with the ground truth. There are certain limitations to the TIM that would not allow for a particular work zone to be marked as active during a certain time of day, or switch between multiple lanes within the same geometry to be marked as being under construction and assigned diversions. To mitigate this problem, an update to the standard is currently under development by adding a roadside safety message. This message aims to address any such shortfalls and enhance overall work zone safety. Future updates to V2X Hub and CAVe-in-a-box may attempt to incorporate any improvements through the open-source effort.

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